1. Field of the Invention
The invention is in the field of polymer chemistry. More particularly, it concerns polymers having active methylene groups that may be used as reactive sites.
2. Prior Art
The concept of a polymer which provides a plurality of sites for reaction or coupling is well known. Most commonly, the active sites on such polymers are amines, alcohols, acids or some other heteroatom functionality that can serve as a coupling or reaction site. The following commonly assigned patents show such materials: U.S. Pat. No. 4,182,885 of Bunes shows that amine groups of a polymeric or copolymeric amine will couple to a haloanthraquinone under the influence of a copper catalyst. U.S. Pat. No. 4,169,203 of Wingard et al shows that amine groups of a polymeric amine can be acetylated to give acetamides. Probably more in point to the present invention, U.S. Pat. Nos. 4,190,716 of Parkinson et al and 3,920,855 of Dawson et al respectively show that certain types of azo-group bearing polymeric drugs and dyes can be constructed on polymeric backbones. These dyes and drugs are prepared by forming a polymeric aromatic amine, diazotizing the amino groups and then coupling this polymeric diazonium compound to units of an active carbon-bearing aromatic. This process can work well in many preparations. However, it will be appreciated that some specific couplings are not possible, especially when the aromatic desired to be coupled has groups that sterically block or deactivate the specific location sought to be the active site. For example, U.S. Pat. No. 4,190,716 shows that a polymeric azo prodrug of the pharmaceutical, 5-aminosalicylic acid can be formed by coupling salicylic acid to a diazotized aromatic backbone i.e. ##STR3##
The hydroxyl group activates the 5-position carbon; this results in the coupling being essentially exclusively in that position. While this activation is ideal in the case just described, it is most unfortunate if another isomer, such as one coupled at the 4 position, is desired. It was sought to make the 4-aminosalicylic acid analog of the above-described 5-aminosalicylic acid-releasing polymers. 4-Aminosalycylic acid is a well known pharmaceutical and such a polymer would be advantageous. Use of the chemistry taught by U.S. Pat. No. 4,190,716 failed to give the desired product. Neither did variations of that chemistry.
What is needed is a process and polymer that would provide a plurality of active methylene sites which can serve as points for facile attachment of molecules already containing active groups (e.g. diazonium groups, carbonyl groups, etc.).